Improvement of Transverse Corner Cracks in Continuously Cast Hypoperitectic Slabs

Abstract

Solidification proceeds inhomogeneously in hypoperitictic steels (medium carbon steels) with carbon contents in the range of 0.08 to 0.16%. Therefore, longitudinal and transverse cracks easily occur on the slabs in molds. Soft cooling in mold, improvement of the mold powder and decrease of the amount of secondary cooling water have been carried out to prevent these surface cracks. In the slabs cast at Kakogawa Work's No.3 CCM, transverse corner cracks have been found on the slabs with. increase in casting velocity. The cracks occur along deep oscillation marks. Mold powder component and segregation of Mn and P are detected in the vicinity of the cracks. This suggests that these cracks are generated in mold. The mechanism of crack formation is considered from analysis of the relation between transverse corner crack frequency and casting conditions. Based on the analysis, the transverse corner cracks are successfully prevented by such means as supression of the meniscus level fluctuation of molten steel, increase of the mold powder consumption and optimization of the taper on narrow face of mold.